Main feature of modern mining dump trucks is the need to ensure the transportation of minerals with minimal costs, which is achieved by deepening the quarries (in order to save overburden), increasing the slopes of roads, reducing the distance of cargo transportation, increasing the load capacity of machines and improving the safety of their movement. It is shown that new work conditions of dump trucks and major specific requirements are resolved mainly at the stage of layout of machines by optimizing wheel arrangement of dump trucks, loading of tires and their performance, providing specific power of the propulsion system, choice of the transmission type and its units, and major systems to ensure operational safety: brakes, steering, stability of motion. Special attention is paid to the creation of a new system for improving lateral stability and its design for dump trucks with a load capacity of more than 400 t. The results of operational studies of the main layout and design solutions adopted for a dump truck with a load capacity of 450 t are presented. Efficiency of the decisions made is shown which made it possible to create a mining dump truck superior to all analogues in the world by indicators of the main operational properties that ensure competitiveness: fuel efficiency, performance, and operating costs. A system created for the first time for increasing lateral stability (schematic diagram and structural elements) confirmed the projected traffic safety in typical quarries and the necessary life in operation.

The experience of using known and new steels to improve the manufacturability and strength of the main parts of machines, hardened by nitriding, is generalized. New approaches to manufacture of gear wheels hardened by nitriding, both when using aluminum-containing steels and a new material, steel 40ХМФА, are considered. To improve the efficiency and man ufacturability of parts production from aluminum-containing steel 38Х2МЮА, widely used in mechanical engineering, a fundamentally new technology of preliminary heat treatment of workpieces of parts – “incomplete hardening” has been developed, which provides both an increase in the machinability and accuracy of large-sized gear wheels, and an increase in strength due to the elimination of the brittleness of nitrided layer. The high hardness of the nitrided surface of the parts – up to 900 HV – also ensures high wear resistance of the parts. Gear wheels made of new aluminum-containing steel 20ХН4МФЮА solidified at the nitriding stage, have strength characteristics equal to cemented parts, which allows not only increasing the bearing capacity of a number of products, but significant simplification of the technology of manufacturing precise parts that are complex in shape, replacing carburizing with nitriding, thereby eliminating the necessary after-carburizing finishing operation – grinding. Steel 40ХМФА, which does not contain aluminum, has increased heat resistance, hardenability and machinability of parts, as well as the characteristics of their hardened layer. The nitrided layer of gears 0.5–0.7 mm thick does not contain brittle components, which, with a core hardness of 300–320 HB, excludes its “flaking” and subsequent destruction of parts. The use of 40ХМФА steel makes it possible to solve the problems of reliability and service life of large-sized nitrided gears, but it is also promising for the entire range of gears with internal gearing, as well as parts of movable spline gearings. These characteristics also in some cases allow replacing the carburizing of gears (modulus less than 4 mm) by nitriding when using 40ХМФА steel.

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The analysis of the used steels for nitrided parts is carried out. On the basis of a new methodology for increasing the strength of structural steels and parts, new scientific approaches and practical solutions are proposed and considered for the creation of gear wheels strengthened by nitriding both when using aluminum containing steels and a new material, 40ХМФА (40KhMFA) steel, that does not contain aluminum. To improve the efficiency and manufacturability of parts production from aluminum-containing 38Х2МЮА (38Kh2MYuA) steel, widely used in mechanical engineering, a fundamentally new technology of preliminary heat treatment of part blanks, “incomplete quenching”, has been developed, which provides both an increase in the machinability and accuracy of large-sized gear wheels, and an increase in strength due to the elimination of flaking of nitrided layer. The research results are presented on 40ХМФА (40KhMFA) steel, which does not contain aluminum, has increased heat resistance, hardenability and workability of parts, as well as the characteristics of the hardened layer. The nitrided layer of gears with a thickness of 0.5–0.7 mm does not contain brittle components, which, with a core hardness of 300–320 HB, also excludes its flaking and subsequent destruction of parts. The use of 40ХМФА (40KhMFA) steel makes it possible to solve the problems of reliability and life of large-sized nitrided gears, but it is also promising for the entire range of gears with internal gearing, as well as parts of movable spline gearings and fine-modular gears in order to replace carburizing with nitriding.